Malware is the malicious software. Generally, such malware is infiltrated into a computer by being as a file. The infiltrated malware causes a malfunction of the computer by disturbing computer operations, or functions as an information leakage path allowing the personal information of a user to be externally leaked from the computer. As such, it is necessary to delete or modify a file after an inspection for determining whether the file is malware, in order to prevent the damage caused by the malware.
Conventionally, a signature is used to detect malware or determine whether an inspection target file is malware. More particularly, a value, such as a hash value or CRC (Cyclic Redundancy Check) value, representing characteristics of a file is derived from a part of the file which has been known as malware and is stored in a data base. If a target file to be inspected about infection with malware is received, a signature is derived from the target file in the same way as the above and is compared with the previously derived signatures of files including the malware, thereby determining whether the target file is malware.